The 1:1 adduct of gallane (gallium hydride) and trimethylamine is known. Its preparation is taught in Shriver, et al., "Trihydrido(trimethylamine)gallium", Inorganic Syntheses, Vol. 17, pages 42-44 (1980). Preparation of the lithium gallium hydride starting material recited in the foregoing article is taught in Skirk, et al., "Lithium tetrahydridogallate," Inorganic Syntheses, Vol. 17, pages 45-47 (1980). No use for the adduct is reported in these articles. The adduct has a melting point of 69.degree. C., and is sublimable. Consequently, it is not an ideal candidate for use in metal organic chemical vapor deposition (MOCVD), for which compounds in liquid form at or near room temperature are desired. Also, higher alkyl compounds analogous to this adduct are not known.
Gallium arsenide, gallium phosphide, and related compounds have previously been produced by introducing trimethylgallium and arsine (AsH.sub.3) or phosphine (PH.sub.3) to a substrate in a heated deposition chamber of MOCVD (metal organic chemical vapor deposition) apparatus. At the deposition temperature, the source compounds decompose and react at the surface of the substrate to form a gallium arsenide or gallium phosphide film.
A similar reaction in which the arsine or phosphine of the prior art are replaced by alkyl arsenic hydride or alkyl phosphorus hydride is described in U.S. Ser. No. 828,467, filed Feb. 10, 1986 and owned in common with the present application. (That application is hereby incorporated herein by reference.)
One disadvantage of the prior art technique in which arsine or phosphine are used as the Group V element sources is that these source compounds are gaseous and extremely toxic; consequently they are extremely expensive and potentially hazardous to handle. Use of trialkyl arsine and trialkyl phosphine in conjunction with trialkyl gallium for forming III-V films has the disadvantage of not providing any source of monatomic hydrogen. Monatomic hydrogen can combine with the alkyl radicals released during decomposition to form gaseous carbon reaction products such as methane, ethane, ethylene, and the like, which can be transported out of the deposition chamber. If monatomic hydrogen is not present, the alkyl radicals released during decomposition of the source compounds contribute to carbon contamination of the desired film.
Matloubian, et al., "MOCVD Epitaxial Growth of Single Crystal GaN, AlN, and AL.sub.x Ga.sub.1-x N," Journal of Electronic Materials, Vol. 14, No. 5, pp 633-644 (1985) teaches conditions under which gallium nitride films and other films of III-V compounds have been grown using MOCVD.